The purpose of the intracoronary study is to determine the mechanism of action of milrinone, an investigational phosphodiesterase inhibitor, in patients with severe congestive heart failure. In addition, the protocol has been expanded to study the pharmacology of dobutamine, a beta- adrenergic agonist, in patients with heart failure and beta-adrenergic desensitization. Patients who have completed the acute intracoronary protocol are followed during chronic oral therapy with milrinone.